Abstract:

Background: High amounts of astrocytes co-localise with fibrillar As-plaques in post-mortem AD brains. It is
therefore of great interest to develop a PET tracer for visualising reactive astrocytes in Alzheimer's diseasefs
earliest stages and study the regional distribution in brain in comparison to fibrillar As. Monoamine oxidase-B
(MAO-B) is found primarily in astrocytes. 11C-L-deterium-deprenyl (DED) is a PET tracer with high affinity and
specificity for MAO-B. In the current investigation we performed DED-, PIB- and FDG-PET in a group of MCI and
AD patients to evaluate the inter-relationship between the three tracers.

Results: ANOVA on the regional DED binding data revealed a significant group effect in the bilateral frontal and
bilateral parietal cortices. Increased DED binding in most cortical and sub-cortical regions was observed in the
MCI patients relative to the controls and AD patients. All patients, except three MCI, were PIB+. Limited regional
correlations were found between the three PET tracers particularly between DED and PIB.

Conclusions: Increased DED binding throughout the brain of the MCI patients might suggest that astrocytosis is
an early phenomenon in AD development. DED-PET did not correlate with FDG or PIB in most brain regions. To
better understand the lack of a strong relationship between the tracers, particularly DED and PIB, requires further
investigation with parallel neuroimaging and postmortem studies.